Twin Tunnels widening cost balloons to $100M

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With the preliminary work for the Twin Tunnels widening project under way, transportation officials are realizing they're in for nearly double the money originally anticipated.

The total bill to blast open the eastbound tunnel bore near Idaho Springs on Interstate 70 allowing for a third highway lane is now expected to reach $100 million. The Colorado Department of Transportation initially budgeted $60 million for the project, but is still moving forward with the work.

"We felt we were committed to the project," said Doug Aden, a member of the Colorado Transportation Commission, the body that approved the additional funding. "We were concerned about the substantial increase in cost, but ... any time you start tunneling, you get into a lot of things you don't know you're going to get into. We just felt it was a critical project and needed to move ahead."

The extra cash will be pulled out of the transportation commission's reserves.

Even with design work in the early stages, it quickly became clear the money set aside for the project wouldn't nearly cover the costs, CDOT officials said. Increasing the size of the eastbound tunnel bore was initially expected to cost $25 million. It is now on track to top $45 million, and crews are also having to makeover a nearby frontage road to accommodate detoured highway traffic during the project.

"We had to just come to the reality that it's impossible to make the $60 million work," CDOT project manager Jim Bemelen said.

Though the transportation commission will shell out most of the extra money, CDOT's Region 1, which includes Summit County, will also kick in to make up the difference by postponing other projects. one planned project was cancelled altogether.

"We did some reprioritizations in Region 1," Bemelen said.

The tunnel widening is intended to expand the highway to three lanes from Idaho Springs all the way into Denver, helping to improve the flow of heavy weekend and holiday tourist traffic to and from the mountains. The widening is the first in a series of projects planned to reduce traffic on the I-70 mountain corridor.

New lanes, paid for with tolls, may also be part of the effort. CDOT will be paying early next year for another study on the I-70 mountain corridor that transportation officials say is necessary to determine the possible financial power of tolling lanes on I-70.

"This is not throwaway work," Bemelen said. "This study is getting closer to looking to see if there's ... a financially feasible and politically acceptable project to be had."

Transportation officials rejected two different proposals for co-development projects from private engineering firms recently, but say the traffic and revenue study will determine whether a private partner might be able to front the money for an extensive improvement project on the interstate, and then see a return on investment through tolls.

The study has the support of local officials tuned into discussions regarding the highway's future.

"This traffic and revenue study is crucial to determining what is remotely possible on the I-70 mountain corridor," Summit County Commissioner Dan Gibbs said. "It allows CDOT, in my opinion, to keep its options open and to be more flexible in terms of co-developments down the road."

The $5 million study is set to begin early next year and will likely take approximately nine months to complete.